Qt: Silence a bogus warning printed when using the debug runtime

The Qt debug runtime prints a bogus warning on the console if you
haven't called makeCurrent since the last time you called swapBuffers.
This presumably means something if you're using QGLWidget the "regular"
way, but in our multi-threaded use case is harmless since we never call
doneCurrent in the rendering thread.

src/citra_qt/bootmanager.cpp

@@ -138,7 +138,13 @@ void GRenderWindow::moveContext()
 
 void GRenderWindow::SwapBuffers()
 {
-    // MakeCurrent is already called in renderer_opengl
+#if !defined(QT_NO_DEBUG)
+    // Qt debug runtime prints a bogus warning on the console if you haven't called makeCurrent
+    // since the last time you called swapBuffers. This presumably means something if you're using
+    // QGLWidget the "regular" way, but in our multi-threaded use case is harmless since we never
+    // call doneCurrent in this thread.
+    child->makeCurrent();
+#endif
     child->swapBuffers();
 }